Unify the flags for rmaps and page tracking data, using a
single flag in struct kvm_arch and a single loop to go
over all the address spaces and memslots. This avoids
code duplication between alloc_all_memslots_rmaps and
kvm_page_track_enable_mmu_write_tracking.
Signed-off-by: David Stevens <stevensd@chromium.org>
[This patch is the delta between David's v2 and v3, with conflicts
fixed and my own commit message. - Paolo]
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To date, VMM-directed TSC synchronization and migration has been a bit
messy. KVM has some baked-in heuristics around TSC writes to infer if
the VMM is attempting to synchronize. This is problematic, as it depends
on host userspace writing to the guest's TSC within 1 second of the last
write.
A much cleaner approach to configuring the guest's views of the TSC is to
simply migrate the TSC offset for every vCPU. Offsets are idempotent,
and thus not subject to change depending on when the VMM actually
reads/writes values from/to KVM. The VMM can then read the TSC once with
KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when
the guest is paused.
Cc: David Matlack <dmatlack@google.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210916181538.968978-8-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Protect the reference point for kvmclock with a seqcount, so that
kvmclock updates for all vCPUs can proceed in parallel. Xen runstate
updates will also run in parallel and not bounce the kvmclock cacheline.
Of the variables that were protected by pvclock_gtod_sync_lock,
nr_vcpus_matched_tsc is different because it is updated outside
pvclock_update_vm_gtod_copy and read inside it. Therefore, we
need to keep it protected by a spinlock. In fact it must now
be a raw spinlock, because pvclock_update_vm_gtod_copy, being the
write-side of a seqcount, is non-preemptible. Since we already
have tsc_write_lock which is a raw spinlock, we can just use
tsc_write_lock as the lock that protects the write-side of the
seqcount.
Co-developed-by: Oliver Upton <oupton@google.com>
Message-Id: <20210916181538.968978-6-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Handling the migration of TSCs correctly is difficult, in part because
Linux does not provide userspace with the ability to retrieve a (TSC,
realtime) clock pair for a single instant in time. In lieu of a more
convenient facility, KVM can report similar information in the kvm_clock
structure.
Provide userspace with a host TSC & realtime pair iff the realtime clock
is based on the TSC. If userspace provides KVM_SET_CLOCK with a valid
realtime value, advance the KVM clock by the amount of elapsed time. Do
not step the KVM clock backwards, though, as it is a monotonic
oscillator.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210916181538.968978-5-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Avoid allocating the gfn_track arrays if nothing needs them. If there
are no external to KVM users of the API (i.e. no GVT-g), then page
tracking is only needed for shadow page tables. This means that when tdp
is enabled and there are no external users, then the gfn_track arrays
can be lazily allocated when the shadow MMU is actually used. This avoid
allocations equal to .05% of guest memory when nested virtualization is
not used, if the kernel is compiled without GVT-g.
Signed-off-by: David Stevens <stevensd@chromium.org>
Message-Id: <20210922045859.2011227-3-stevensd@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
By switching from kfree() to kvfree() in kvm_arch_free_vm() Arm64 can
use the common variant. This can be accomplished by adding another
macro __KVM_HAVE_ARCH_VM_FREE, which will be used only by x86 for now.
Further simplification can be achieved by adding __kvm_arch_free_vm()
doing the common part.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-Id: <20210903130808.30142-5-jgross@suse.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Pass struct kvm_page_fault to mmu->page_fault() instead of
extracting the arguments from the struct. FNAME(page_fault) can use
the precomputed bools from the error code.
Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Updates to the kvmclock parameters needs to do a complicated dance of
KVM_REQ_MCLOCK_INPROGRESS and KVM_REQ_CLOCK_UPDATE in addition to taking
pvclock_gtod_sync_lock. Place that in two functions that can be called
on all of master clock update, KVM_SET_CLOCK, and Hyper-V reenlightenment.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Open code the call to mmu->translate_gpa() when loading nested PDPTRs and
kill off the existing helper, kvm_read_guest_page_mmu(), to discourage
incorrect use. Reading guest memory straight from an L2 GPA is extremely
rare (as evidenced by the lack of users), as very few constructs in x86
specify physical addresses, even fewer are virtualized by KVM, and even
fewer yet require emulation of L2 by L0 KVM.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210831164224.1119728-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
KVM_MAX_VCPU_ID is not specifying the highest allowed vcpu-id, but the
number of allowed vcpu-ids. This has already led to confusion, so
rename KVM_MAX_VCPU_ID to KVM_MAX_VCPU_IDS to make its semantics more
clear
Suggested-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210913135745.13944-3-jgross@suse.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
kvm_make_vcpus_request_mask() already disables preemption so just like
kvm_make_all_cpus_request_except() it can be switched to using
pre-allocated per-cpu cpumasks. This allows for improvements for both
users of the function: in Hyper-V emulation code 'tlb_flush' can now be
dropped from 'struct kvm_vcpu_hv' and kvm_make_scan_ioapic_request_mask()
gets rid of dynamic allocation.
cpumask_available() checks in kvm_make_vcpu_request() and
kvm_kick_many_cpus() can now be dropped as they checks for an impossible
condition: kvm_init() makes sure per-cpu masks are allocated.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210903075141.403071-9-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Support for 710 VCPUs was tested by Red Hat since RHEL-8.4,
so increase KVM_SOFT_MAX_VCPUS to 710.
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20210903211600.2002377-4-ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Increase KVM_MAX_VCPUS to 1024, so we can test larger VMs.
I'm not changing KVM_SOFT_MAX_VCPUS yet because I'm afraid it
might involve complicated questions around the meaning of
"supported" and "recommended" in the upstream tree.
KVM_SOFT_MAX_VCPUS will be changed in a separate patch.
For reference, visible effects of this change are:
- KVM_CAP_MAX_VCPUS will now return 1024 (of course)
- Default value for CPUID[HYPERV_CPUID_IMPLEMENT_LIMITS (00x40000005)].EAX
will now be 1024
- KVM_MAX_VCPU_ID will change from 1151 to 4096
- Size of struct kvm will increase from 19328 to 22272 bytes
(in x86_64)
- Size of struct kvm_ioapic will increase from 1780 to 5084 bytes
(in x86_64)
- Bitmap stack variables that will grow:
- At kvm_hv_flush_tlb() kvm_hv_send_ipi(),
vp_bitmap[] and vcpu_bitmap[] will now be 128 bytes long
- vcpu_bitmap at bioapic_write_indirect() will be 128 bytes long
once patch "KVM: x86: Fix stack-out-of-bounds memory access
from ioapic_write_indirect()" is applied
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20210903211600.2002377-3-ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Instead of requiring KVM_MAX_VCPU_ID to be manually increased
every time we increase KVM_MAX_VCPUS, set it to 4*KVM_MAX_VCPUS.
This should be enough for CPU topologies where Cores-per-Package
and Packages-per-Socket are not powers of 2.
In practice, this increases KVM_MAX_VCPU_ID from 1023 to 1152.
The only side effect of this change is making some fields in
struct kvm_ioapic larger, increasing the struct size from 1628 to
1780 bytes (in x86_64).
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20210903211600.2002377-2-ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When the 5-level page table CPU flag is set in the host, but the guest
has CR4.LA57=0 (including the case of a 32-bit guest), the top level of
the shadow NPT page tables will be fixed, consisting of one pointer to
a lower-level table and 511 non-present entries. Extend the existing
code that creates the fixed PML4 or PDP table, to provide a fixed PML5
table if needed.
This is not needed on EPT because the number of layers in the tables
is specified in the EPTP instead of depending on the host CR4.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
Message-Id: <20210818165549.3771014-3-wei.huang2@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
AMD future CPUs will require a 5-level NPT if host CR4.LA57 is set.
To prevent kvm_mmu_get_tdp_level() from incorrectly changing NPT level
on behalf of CPUs, add a new parameter in kvm_configure_mmu() to force
a fixed TDP level.
Signed-off-by: Wei Huang <wei.huang2@amd.com>
Message-Id: <20210818165549.3771014-2-wei.huang2@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
KVM_GUESTDBG_BLOCKIRQ will allow KVM to block all interrupts
while running.
This change is mostly intended for more robust single stepping
of the guest and it has the following benefits when enabled:
* Resuming from a breakpoint is much more reliable.
When resuming execution from a breakpoint, with interrupts enabled,
more often than not, KVM would inject an interrupt and make the CPU
jump immediately to the interrupt handler and eventually return to
the breakpoint, to trigger it again.
From the user point of view it looks like the CPU never executed a
single instruction and in some cases that can even prevent forward
progress, for example, when the breakpoint is placed by an automated
script (e.g lx-symbols), which does something in response to the
breakpoint and then continues the guest automatically.
If the script execution takes enough time for another interrupt to
arrive, the guest will be stuck on the same breakpoint RIP forever.
* Normal single stepping is much more predictable, since it won't
land the debugger into an interrupt handler.
* RFLAGS.TF has less chance to be leaked to the guest:
We set that flag behind the guest's back to do single stepping
but if single step lands us into an interrupt/exception handler
it will be leaked to the guest in the form of being pushed
to the stack.
This doesn't completely eliminate this problem as exceptions
can still happen, but at least this reduces the chances
of this happening.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210811122927.900604-6-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Existing KVM code tracks the number of large pages regardless of their
sizes. Therefore, when large page of 1GB (or larger) is adopted, the
information becomes less useful because lpages counts a mix of 1G and 2M
pages.
So remove the lpages since it is easy for user space to aggregate the info.
Instead, provide a comprehensive page stats of all sizes from 4K to 512G.
Suggested-by: Ben Gardon <bgardon@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
Cc: Jing Zhang <jingzhangos@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: Sean Christopherson <seanjc@google.com>
Message-Id: <20210803044607.599629-4-mizhang@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
APICV_INHIBIT_REASON_HYPERV is currently unconditionally forced upon
SynIC activation as SynIC's AutoEOI is incompatible with APICv/AVIC. It is,
however, possible to track whether the feature was actually used by the
guest and only inhibit APICv/AVIC when needed.
TLFS suggests a dedicated 'HV_DEPRECATING_AEOI_RECOMMENDED' flag to let
Windows know that AutoEOI feature should be avoided. While it's up to
KVM userspace to set the flag, KVM can help a bit by exposing global
APICv/AVIC enablement.
Maxim:
- always set HV_DEPRECATING_AEOI_RECOMMENDED in kvm_get_hv_cpuid,
since this feature can be used regardless of AVIC
Paolo:
- use arch.apicv_update_lock to protect the hv->synic_auto_eoi_used
instead of atomic ops
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210810205251.424103-12-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Currently on SVM, the kvm_request_apicv_update toggles the APICv
memslot without doing any synchronization.
If there is a mismatch between that memslot state and the AVIC state,
on one of the vCPUs, an APIC mmio access can be lost:
For example:
VCPU0: enable the APIC_ACCESS_PAGE_PRIVATE_MEMSLOT
VCPU1: access an APIC mmio register.
Since AVIC is still disabled on VCPU1, the access will not be intercepted
by it, and neither will it cause MMIO fault, but rather it will just be
read/written from/to the dummy page mapped into the
APIC_ACCESS_PAGE_PRIVATE_MEMSLOT.
Fix that by adding a lock guarding the AVIC state changes, and carefully
order the operations of kvm_request_apicv_update to avoid this race:
1. Take the lock
2. Send KVM_REQ_APICV_UPDATE
3. Update the apic inhibit reason
4. Release the lock
This ensures that at (2) all vCPUs are kicked out of the guest mode,
but don't yet see the new avic state.
Then only after (4) all other vCPUs can update their AVIC state and resume.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210810205251.424103-10-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Thanks to the former patches, it is now possible to keep the APICv
memslot always enabled, and it will be invisible to the guest
when it is inhibited
This code is based on a suggestion from Sean Christopherson:
https://lkml.org/lkml/2021/7/19/2970
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210810205251.424103-9-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Introduce kvm_mmu_slot_lpages() to calculcate lpage_info and rmap array size.
The other __kvm_mmu_slot_lpages() can take an extra parameter of npages rather
than fetching from the memslot pointer. Start to use the latter one in
kvm_alloc_memslot_metadata().
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210730220455.26054-4-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the declaration of kvm_spurious_fault() to KVM's "private" x86.h,
it should never be called by anything other than low level KVM code.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
[sean: rebased to a series without __ex()/__kvm_handle_fault_on_reboot()]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210809173955.1710866-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Remove the __kvm_handle_fault_on_reboot() and __ex() macros now that all
VMX and SVM instructions use asm goto to handle the fault (or in the
case of VMREAD, completely custom logic). Drop kvm_spurious_fault()'s
asmlinkage annotation as __kvm_handle_fault_on_reboot() was the only
flow that invoked it from assembly code.
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Like Xu <like.xu.linux@gmail.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210809173955.1710866-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Commit ae561edeb4 ("KVM: x86: DR0-DR3 are not clear on reset") added code to
ensure eff_db are updated when they're modified through non-standard paths.
But there is no reason to also update hardware DRs unless hardware breakpoints
are active or DR exiting is disabled, and in those cases updating hardware is
handled by KVM_DEBUGREG_WONT_EXIT and KVM_DEBUGREG_BP_ENABLED.
KVM_DEBUGREG_RELOAD just causes unnecesarry load of hardware DRs and is better
to be removed.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20210809174307.145263-1-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add yet another spinlock for the TDP MMU and take it when marking indirect
shadow pages unsync. When using the TDP MMU and L1 is running L2(s) with
nested TDP, KVM may encounter shadow pages for the TDP entries managed by
L1 (controlling L2) when handling a TDP MMU page fault. The unsync logic
is not thread safe, e.g. the kvm_mmu_page fields are not atomic, and
misbehaves when a shadow page is marked unsync via a TDP MMU page fault,
which runs with mmu_lock held for read, not write.
Lack of a critical section manifests most visibly as an underflow of
unsync_children in clear_unsync_child_bit() due to unsync_children being
corrupted when multiple CPUs write it without a critical section and
without atomic operations. But underflow is the best case scenario. The
worst case scenario is that unsync_children prematurely hits '0' and
leads to guest memory corruption due to KVM neglecting to properly sync
shadow pages.
Use an entirely new spinlock even though piggybacking tdp_mmu_pages_lock
would functionally be ok. Usurping the lock could degrade performance when
building upper level page tables on different vCPUs, especially since the
unsync flow could hold the lock for a comparatively long time depending on
the number of indirect shadow pages and the depth of the paging tree.
For simplicity, take the lock for all MMUs, even though KVM could fairly
easily know that mmu_lock is held for write. If mmu_lock is held for
write, there cannot be contention for the inner spinlock, and marking
shadow pages unsync across multiple vCPUs will be slow enough that
bouncing the kvm_arch cacheline should be in the noise.
Note, even though L2 could theoretically be given access to its own EPT
entries, a nested MMU must hold mmu_lock for write and thus cannot race
against a TDP MMU page fault. I.e. the additional spinlock only _needs_ to
be taken by the TDP MMU, as opposed to being taken by any MMU for a VM
that is running with the TDP MMU enabled. Holding mmu_lock for read also
prevents the indirect shadow page from being freed. But as above, keep
it simple and always take the lock.
Alternative #1, the TDP MMU could simply pass "false" for can_unsync and
effectively disable unsync behavior for nested TDP. Write protecting leaf
shadow pages is unlikely to noticeably impact traditional L1 VMMs, as such
VMMs typically don't modify TDP entries, but the same may not hold true for
non-standard use cases and/or VMMs that are migrating physical pages (from
L1's perspective).
Alternative #2, the unsync logic could be made thread safe. In theory,
simply converting all relevant kvm_mmu_page fields to atomics and using
atomic bitops for the bitmap would suffice. However, (a) an in-depth audit
would be required, (b) the code churn would be substantial, and (c) legacy
shadow paging would incur additional atomic operations in performance
sensitive paths for no benefit (to legacy shadow paging).
Fixes: a2855afc7e ("KVM: x86/mmu: Allow parallel page faults for the TDP MMU")
Cc: stable@vger.kernel.org
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210812181815.3378104-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
gfn_to_hva_cache is not thread-safe, so it is usually used only within
a vCPU (whose code is protected by vcpu->mutex). The Xen interface
implementation has such a cache in kvm->arch, but it is not really
used except to store the location of the shared info page. Replace
shinfo_set and shinfo_cache with just the value that is passed via
KVM_XEN_ATTR_TYPE_SHARED_INFO; the only complication is that the
initialization value is not zero anymore and therefore kvm_xen_init_vm
needs to be introduced.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Based on our observations, after any vm-exit associated with vPMU, there
are at least two or more perf interfaces to be called for guest counter
emulation, such as perf_event_{pause, read_value, period}(), and each one
will {lock, unlock} the same perf_event_ctx. The frequency of calls becomes
more severe when guest use counters in a multiplexed manner.
Holding a lock once and completing the KVM request operations in the perf
context would introduce a set of impractical new interfaces. So we can
further optimize the vPMU implementation by avoiding repeated calls to
these interfaces in the KVM context for at least one pattern:
After we call perf_event_pause() once, the event will be disabled and its
internal count will be reset to 0. So there is no need to pause it again
or read its value. Once the event is paused, event period will not be
updated until the next time it's resumed or reprogrammed. And there is
also no need to call perf_event_period twice for a non-running counter,
considering the perf_event for a running counter is never paused.
Based on this implementation, for the following common usage of
sampling 4 events using perf on a 4u8g guest:
echo 0 > /proc/sys/kernel/watchdog
echo 25 > /proc/sys/kernel/perf_cpu_time_max_percent
echo 10000 > /proc/sys/kernel/perf_event_max_sample_rate
echo 0 > /proc/sys/kernel/perf_cpu_time_max_percent
for i in `seq 1 1 10`
do
taskset -c 0 perf record \
-e cpu-cycles -e instructions -e branch-instructions -e cache-misses \
/root/br_instr a
done
the average latency of the guest NMI handler is reduced from
37646.7 ns to 32929.3 ns (~1.14x speed up) on the Intel ICX server.
Also, in addition to collecting more samples, no loss of sampling
accuracy was observed compared to before the optimization.
Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20210728120705.6855-1-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
As alluded to in commit f36f3f2846 ("KVM: add "new" argument to
kvm_arch_commit_memory_region"), a bunch of other places where struct
kvm_memory_slot is used, needs to be refactored to preserve the
"const"ness of struct kvm_memory_slot across-the-board.
Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
Message-Id: <20210713023338.57108-1-someguy@effective-light.com>
[Do not touch body of slot_rmap_walk_init. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the EDX initialization at vCPU RESET, which is now identical between
VMX and SVM, into common code.
No functional change intended.
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-20-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a new statistic max_mmu_rmap_size, which stores the maximum size of rmap
for the vm.
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210625153214.43106-2-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This better reflects the purpose of this variable on AMD, since
on AMD the AVIC's memory slot can be enabled and disabled dynamically.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210623113002.111448-4-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a fallback mechanism to the in-kernel instruction emulator that
allows userspace the opportunity to process an instruction the emulator
was unable to. When the in-kernel instruction emulator fails to process
an instruction it will either inject a #UD into the guest or exit to
userspace with exit reason KVM_INTERNAL_ERROR. This is because it does
not know how to proceed in an appropriate manner. This feature lets
userspace get involved to see if it can figure out a better path
forward.
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Message-Id: <20210510144834.658457-2-aaronlewis@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop the pre-computed last_nonleaf_level, which is arguably wrong and at
best confusing. Per the comment:
Can have large pages at levels 2..last_nonleaf_level-1.
the intent of the variable would appear to be to track what levels can
_legally_ have large pages, but that intent doesn't align with reality.
The computed value will be wrong for 5-level paging, or if 1gb pages are
not supported.
The flawed code is not a problem in practice, because except for 32-bit
PSE paging, bit 7 is reserved if large pages aren't supported at the
level. Take advantage of this invariant and simply omit the level magic
math for 64-bit page tables (including PAE).
For 32-bit paging (non-PAE), the adjustments are needed purely because
bit 7 is ignored if PSE=0. Retain that logic as is, but make
is_last_gpte() unique per PTTYPE so that the PSE check is avoided for
PAE and EPT paging. In the spirit of avoiding branches, bump the "last
nonleaf level" for 32-bit PSE paging by adding the PSE bit itself.
Note, bit 7 is ignored or has other meaning in CR3/EPTP, but despite
FNAME(walk_addr_generic) briefly grabbing CR3/EPTP in "pte", they are
not PTEs and will blow up all the other gpte helpers.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-51-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Expand the comments for the MMU roles. The interactions with gfn_track
PGD reuse in particular are hairy.
Regarding PGD reuse, add comments in the nested virtualization flows to
call out why kvm_init_mmu() is unconditionally called even when nested
TDP is used.
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-50-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop kvm_mmu.nx as there no consumers left.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-39-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Rename "nxe" to "efer_nx" so that future macro magic can use the pattern
<reg>_<bit> for all CR0, CR4, and EFER bits that included in the role.
Using "efer_nx" also makes it clear that the role bit reflects EFER.NX,
not the NX bit in the corresponding PTE.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-25-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop MAXPHYADDR from mmu_role now that all MMUs have their role
invalidated after a CPUID update. Invalidating the role forces all MMUs
to re-evaluate the guest's MAXPHYADDR, and the guest's MAXPHYADDR can
only be changed only through a CPUID update.
This reverts commit de3ccd26fa.
Cc: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Warn userspace that KVM_SET_CPUID{,2} after KVM_RUN "may" cause guest
instability. Initialize last_vmentry_cpu to -1 and use it to detect if
the vCPU has been run at least once when its CPUID model is changed.
KVM does not correctly handle changes to paging related settings in the
guest's vCPU model after KVM_RUN, e.g. MAXPHYADDR, GBPAGES, etc... KVM
could theoretically zap all shadow pages, but actually making that happen
is a mess due to lock inversion (vcpu->mutex is held). And even then,
updating paging settings on the fly would only work if all vCPUs are
stopped, updated in concert with identical settings, then restarted.
To support running vCPUs with different vCPU models (that affect paging),
KVM would need to track all relevant information in kvm_mmu_page_role.
Note, that's the _page_ role, not the full mmu_role. Updating mmu_role
isn't sufficient as a vCPU can reuse a shadow page translation that was
created by a vCPU with different settings and thus completely skip the
reserved bit checks (that are tied to CPUID).
Tracking CPUID state in kvm_mmu_page_role is _extremely_ undesirable as
it would require doubling gfn_track from a u16 to a u32, i.e. would
increase KVM's memory footprint by 2 bytes for every 4kb of guest memory.
E.g. MAXPHYADDR (6 bits), GBPAGES, AMD vs. INTEL = 1 bit, and SEV C-BIT
would all need to be tracked.
In practice, there is no remotely sane use case for changing any paging
related CPUID entries on the fly, so just sweep it under the rug (after
yelling at userspace).
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Invalidate all MMUs' roles after a CPUID update to force reinitizliation
of the MMU context/helpers. Despite the efforts of commit de3ccd26fa
("KVM: MMU: record maximum physical address width in kvm_mmu_extended_role"),
there are still a handful of CPUID-based properties that affect MMU
behavior but are not incorporated into mmu_role. E.g. 1gb hugepage
support, AMD vs. Intel handling of bit 8, and SEV's C-Bit location all
factor into the guest's reserved PTE bits.
The obvious alternative would be to add all such properties to mmu_role,
but doing so provides no benefit over simply forcing a reinitialization
on every CPUID update, as setting guest CPUID is a rare operation.
Note, reinitializing all MMUs after a CPUID update does not fix all of
KVM's woes. Specifically, kvm_mmu_page_role doesn't track the CPUID
properties, which means that a vCPU can reuse shadow pages that should
not exist for the new vCPU model, e.g. that map GPAs that are now illegal
(due to MAXPHYADDR changes) or that set bits that are now reserved
(PAGE_SIZE for 1gb pages), etc...
Tracking the relevant CPUID properties in kvm_mmu_page_role would address
the majority of problems, but fully tracking that much state in the
shadow page role comes with an unpalatable cost as it would require a
non-trivial increase in KVM's memory footprint. The GBPAGES case is even
worse, as neither Intel nor AMD provides a way to disable 1gb hugepage
support in the hardware page walker, i.e. it's a virtualization hole that
can't be closed when using TDP.
In other words, resetting the MMU after a CPUID update is largely a
superficial fix. But, it will allow reverting the tracking of MAXPHYADDR
in the mmu_role, and that case in particular needs to mostly work because
KVM's shadow_root_level depends on guest MAXPHYADDR when 5-level paging
is supported. For cases where KVM botches guest behavior, the damage is
limited to that guest. But for the shadow_root_level, a misconfigured
MMU can cause KVM to incorrectly access memory, e.g. due to walking off
the end of its shadow page tables.
Fixes: 7dcd575520 ("x86/kvm/mmu: check if tdp/shadow MMU reconfiguration is needed")
Cc: Yu Zhang <yu.c.zhang@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Restore CR4.LA57 to the mmu_role to fix an amusing edge case with nested
virtualization. When KVM (L0) is using TDP, CR4.LA57 is not reflected in
mmu_role.base.level because that tracks the shadow root level, i.e. TDP
level. Normally, this is not an issue because LA57 can't be toggled
while long mode is active, i.e. the guest has to first disable paging,
then toggle LA57, then re-enable paging, thus ensuring an MMU
reinitialization.
But if L1 is crafty, it can load a new CR4 on VM-Exit and toggle LA57
without having to bounce through an unpaged section. L1 can also load a
new CR3 on exit, i.e. it doesn't even need to play crazy paging games, a
single entry PML5 is sufficient. Such shenanigans are only problematic
if L0 and L1 use TDP, otherwise L1 and L2 share an MMU that gets
reinitialized on nested VM-Enter/VM-Exit due to mmu_role.base.guest_mode.
Note, in the L2 case with nested TDP, even though L1 can switch between
L2s with different LA57 settings, thus bypassing the paging requirement,
in that case KVM's nested_mmu will track LA57 in base.level.
This reverts commit 8053f924ca.
Fixes: 8053f924ca ("KVM: x86/mmu: Drop kvm_mmu_extended_role.cr4_la57 hack")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Generic KVM stats are those collected in architecture independent code
or those supported by all architectures; put all generic statistics in
a separate structure. This ensures that they are defined the same way
in the statistics API which is being added, removing duplication among
different architectures in the declaration of the descriptors.
No functional change intended.
Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Signed-off-by: Jing Zhang <jingzhangos@google.com>
Message-Id: <20210618222709.1858088-2-jingzhangos@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This hypercall is used by the SEV guest to notify a change in the page
encryption status to the hypervisor. The hypercall should be invoked
only when the encryption attribute is changed from encrypted -> decrypted
and vice versa. By default all guest pages are considered encrypted.
The hypercall exits to userspace to manage the guest shared regions and
integrate with the userspace VMM's migration code.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Steve Rutherford <srutherford@google.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <90778988e1ee01926ff9cac447aacb745f954c8c.1623174621.git.ashish.kalra@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When emulating INVVPID for L1, free only L2+ roots, using the guest_mode
tag in the MMU role to identify L2+ roots. From L1's perspective, its
own TLB entries use VPID=0, and INVVPID is not requied to invalidate such
entries. Per Intel's SDM, INVVPID _may_ invalidate entries with VPID=0,
but it is not required to do so.
Cc: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609234235.1244004-10-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Drop skip_mmu_sync and skip_tlb_flush from __kvm_mmu_new_pgd() now that
all call sites unconditionally skip both the sync and flush.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609234235.1244004-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Trigger a full TLB flush on behalf of the guest on nested VM-Enter and
VM-Exit when VPID is disabled for L2. kvm_mmu_new_pgd() syncs only the
current PGD, which can theoretically leave stale, unsync'd entries in a
previous guest PGD, which could be consumed if L2 is allowed to load CR3
with PCID_NOFLUSH=1.
Rename KVM_REQ_HV_TLB_FLUSH to KVM_REQ_TLB_FLUSH_GUEST so that it can
be utilized for its obvious purpose of emulating a guest TLB flush.
Note, there is no change the actual TLB flush executed by KVM, even
though the fast PGD switch uses KVM_REQ_TLB_FLUSH_CURRENT. When VPID is
disabled for L2, vpid02 is guaranteed to be '0', and thus
nested_get_vpid02() will return the VPID that is shared by L1 and L2.
Generate the request outside of kvm_mmu_new_pgd(), as getting the common
helper to correctly identify which requested is needed is quite painful.
E.g. using KVM_REQ_TLB_FLUSH_GUEST when nested EPT is in play is wrong as
a TLB flush from the L1 kernel's perspective does not invalidate EPT
mappings. And, by using KVM_REQ_TLB_FLUSH_GUEST, nVMX can do future
simplification by moving the logic into nested_vmx_transition_tlb_flush().
Fixes: 41fab65e7c ("KVM: nVMX: Skip MMU sync on nested VMX transition when possible")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609234235.1244004-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
if new KVM_*_SREGS2 ioctls are used, the PDPTRs are
a part of the migration state and are correctly
restored by those ioctls.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210607090203.133058-9-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Kill off pdptrs_changed() and instead go through the full kvm_set_cr3()
for PAE guest, even if the new CR3 is the same as the current CR3. For
VMX, and SVM with NPT enabled, the PDPTRs are unconditionally marked as
unavailable after VM-Exit, i.e. the optimization is dead code except for
SVM without NPT.
In the unlikely scenario that anyone cares about SVM without NPT _and_ a
PAE guest, they've got bigger problems if their guest is loading the same
CR3 so frequently that the performance of kvm_set_cr3() is notable,
especially since KVM's fast PGD switching means reloading the same CR3
does not require a full rebuild. Given that PAE and PCID are mutually
exclusive, i.e. a sync and flush are guaranteed in any case, the actual
benefits of the pdptrs_changed() optimization are marginal at best.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210607090203.133058-4-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
